So... everything has been replaced. New aisin pump, new rad, and new TESTED t-stat (fully opens at 180F).

I bought it overheating when highway driven. Lower hose was cold and dummy had installed an el cheapo t-stat. I gutted the t-stat along with the water control valve and drove home.

There was a weird bearing kinda noise, so I replaced water pump just in case and t-stat. It still overheated and lower hose was still cold. Some dummy along the line had dumped silver stop leak in it (for rad I guess), so I thought maybe rad was clogged. No dice. I bought a better t-stat and tested it in a pot with an infrared thermometer. No dice. I burped it many times along the way until no bubbles came out whatsoever. I shut the car off after temp goes over 200F and feel the hose. The sucker is cold, but pressurized. There's not a bit of flow. Water pump works extremely well. It will shoot several feet out of the rad when you fire it up lol

HG doesn't leak. There's no new air going into the system and the normal amount of coolant is pushed into the reservoir.

This doesn't make any sense. It's not my 1st rodeo with a VQ. Is there some insane air lock that can happen on 3.0s

 

New hoses installed?

 

I don't waste money on hoses. They're pliable with no defects.

Everything was very clean that I've disassembled, FWIW.

 

Maybe you ought to waste money on hoses. Maybe too pliable.
Have had experience with circulation problems when lower hose
collapses, as well as lower hoses that separate and the inside closes
off the circulation.

 

No, it's a total waste of money. Lower hose doesn't collapse. Nor could it unless you weren't getting flow from the other side. As I said, it's pressurized.

It was fine with t-stat gutted. The big question is why it doesn't work, now.

 

Your wrong!
Didn't want to go into details, but many years ago worked on a Seville diesel, running hot, notorious for head gasket problems. Replaced the heat gaskets, same problem, then found the lower radiator hose, old style with the spring inside, but the spring moved into the radiator leaving the water pump end, behind the A/C bracket empty, and when running the hose pulled shut, I'll repeat collapsed completely. I actually pulled the spring out of the radiator and placed it into the hose fully, car was fine. It was my Seville.

Same problem on an old Chrysler, inside lower hose separated and stopped the circulation. Replaced hose, fine. Son's car.

So these are first hand experiences with collapsed lower radiator hoses, so you had better rethink your stance.

 

You forgetting that those are stupid domestics. I, too, have seen those failed springs. But we're just talking about reinforced, shaped rubber, here. Coolant pours through the hose with no issue.

 

It happens to imports as well, have had an old Camry with similar problem, but upper hose.
Guess what I must ask is, if the water flows fine without the radiator, what is the common denominator when it doesn't? As the water pump is fine, only thing I can think of is what connects to the new rad, hoses.
Good luck.

 

Nissan did an experiment on the 2000 & 2001 engines. They added a "Water Control Valve" on the engine. It is like a 2nd thermostat connecting the 2 banks of the engine just below the cylinder heads. It is on the opposite end of the engine from the regular thermostat.

There isn't a lot of info on this but it can play havoc with the cooling. There have been several threads of people having problems with this.

3.0 engine with Water Control Valve


3.0 engine without Water Control Valve

 

That's why it was gutted originally. It's one less failure point. It's there to heat up the block faster and keep it hot. Worthless. My QR25 has it and I gutted it as well (and used a 170F t-stat).

The ideal solution is to use another 180F for the water control valve, but that's not important right now.

 

When you say gutted, do you mean that that water control passage is now wide open? If so, maybe you should block it, and somehow block the passage between the 2 cylinder banks too. From the FSM diagrams, it looks like that valve is there to try to push more of the hot coolant from the cyl head down into the block, decreasing warm up times, like you said. With it completely blocked, more coolant flows around the top cylinder head and less flow in the block, they way it always is normally on the older VQ30DE.

Also you can see from the diagram, and probably already know, the excess extra hot cylinder head coolant is going to the heater core and throttle body. So a way to test this theory is to see how hot the heater core is getting. If it's not getting too hot, then that shows that not enough coolant is circulating up top, so to speak.

 

Yes, it would be like wide open all the time.

The heads/block are just paths to the return pipe, though. None of that is going to affect return flow through the radiator.

 

big update: I like the idea of insurance fraud for this car.

I swapped back to gutted thermostat and there was a river through the radiator.
So, I swapped an OEM '09 stat into the housing (had a broken 09 laying around).

Guess what? IT DOESN'T ****ING OPEN. So, apparently they work, but not when installed. Just ****ing amazing. That is the most impossible **** thing I've ever seen.

**** this POS, I'm going to bed. It better catch on fire while I'm sleeping.

 

gut the precats

 

I would if it were a 3.5. Of course, I would never buy a high mileage 3.5 with cats unless motor was already blown.
I'm just going to drill a hole in the t-stat and see what happens.

 

You are hard headed. Pan handle for $5.00 bucks to replace that one hose. Sometimes we all over think an issue.

 

hi,

I am having the exact same issue with my Maxima. I was driving from Illinois to California and my car is overheating in Utah. Been stuck here for a few days now and the mechanic is clueless.

Really appreciate if you can tell how you addressed your problem above.